The present invention relates generally to a disposable absorbent article or garment that employs an absorbent composite as one or more of its structural components. Disposable absorbent articles or garments contemplated by the invention include diapers, training pants, adult incontinence products, feminine hygiene products, and other similar use absorbent products (collectively xe2x80x9cdisposable absorbent articlesxe2x80x9d). The use of disposable diapers and training pants has surpassed the use of cloth diapers. Disposable feminine hygiene products are popular because these offer improved comfort and utility to the wearer. Disposable incontinence products, on the other hand, are intended for adults and provide these wearers control and absorption of involuntary bowel and bladder discharge associated with some medical conditions, including those associated with advancing age.
Prior art disposable absorbent articles typically employ three basic structural elements: a fluid permeable topsheet that is placed next to the wearer""s skin when the article is worm, a backsheet which forms the outer surface of the diaper, and an absorbent element interposed between the topsheet and the backsheet. The permeable topsheet is designed to allow liquid to pass from the area adjacent the wearer into the area of the core. Topsheets may be constructed from a wide range of liquid and vapor permeable hydrophilic material, and may be used with surface activation agents (xe2x80x9csurfactantsxe2x80x9d) to increase its liquid permeability. Surfactants lower the surface tension of the liquid and facilitates the liquid""s passage through the topsheet.
The backsheet is typically vapor and liquid impermeable so as to minimize or prevent leakage. For example, the backsheet is often an impermeable film that extends the full width of the article. In some of the more recent designs, a cloth-like outer sheet is added to the film for a more pleasing feel, as the film is positioned to cover only the central portion of the backsheet, and/or in the area most likely to be exposed to liquid. In either design, the film may be made so as to be impermeable or to have some vapor transmission properties, or xe2x80x9cbreathability,xe2x80x9d and functions to contain fluids within the absorbent element. Such a two-layer backsheet design, however, contributes to the complexity of any manufacturing process. The articles further include a middle layer of a moisture absorbent core between the topsheet and backsheet. The absorbent core must be able to take up the liquid which passes through the topsheet, and distribute the liquid. The core is designed to retain the distributed liquid.
A typical absorbent core of the prior art is constructed of two components: a high or super absorbent material and an absorbent matrix. Common sources of absorbent materials include numerous compounds of organic materials such as polyvinyl alcohol, polyacrylates, various grafted starches, and cross-linked sodium polyacrylate. These absorbent materials are employed as core material in the form of particles, fibers, foams, and/or layers. The absorbent matrix, on the other hand, is typically provided by de-fiberized wood pulp or similar material. As expected, the majority volume of a prior art absorbent core is taken up by the absorbent matrix and not the absorbent material.
The two-component core design is used primarily because many of the preferred high absorbent materials are incapable of absorbing liquid at the rate or even near the rate at which liquid is typically received by the absorbent article (when worn). Therefore, the absorbent matrix is provided to hold the received liquid and deliver it to the high absorbency material at a rate slower than the rate at which the liquid would otherwise be delivered (absent the absorbent matrix). This allows the high absorbent material more time to fully absorb the liquid.
Another function of the absorbent matrix is to prevent xe2x80x9cgel blocking.xe2x80x9d Gel blocking is the blockage of the interstitial spaces between elements or particles of the high absorbent material and blockage of channels through which the liquid must pass to encounter unsaturated absorbent particles. Such gel blocking can occur as a result of the high absorbency particles or elements swelling upon absorption of liquid and occupying additional volume. The fibers of the matrix prevent xe2x80x9cgel blockingxe2x80x9d by dispersing the high absorbent particles throughout the matrix, thereby minimizing the potential for particle-to-particle contact.
Although the absorbent matrix does not have the high absorption properties of the high absorbent material, it is recognized as a necessary component in achieving adequate absorbency (measured by both capacity and rate) in prior art core compositions. Achieving optimal absorbency in these core compositions involves not only selecting a suitable high absorbent material, but also identifying the optimal ratio between the high absorbent material and the absorbent matrix. Since the SAP material is typically 2-10 times more absorbent than the pulp material (of the absorbent matrix), one means of providing a thinner, more compact absorbent core is to increase its SAP content and decrease its pulp content. The ratio of SAP content to pulp content is, however, limited by the propensity of higher SAP/pulp ratio compositions to gel block during use. It is generally accepted that an SAP/pulp ratio of 1 is the highest, practical ratio available. Accordingly, this ratio also sets the lower practical limit of the core thickness and thus, of the disposable absorbent article.
It is, therefore, one of multiple objects of the invention to provide a disposable absorbent article or garment employing an improved absorbent composite therein. According to the invention, such an absorbent composite may be employed as a primary component of the absorbent core, backsheet, topsheet, containment walls or cuffs, and other elements (e.g., an acquisition layer) of the disposable absorbent article, or a combination of two or more of these elements, thereby producing an absorbent article having various advantageous characteristics. Among some of the characteristics which may be exhibited by the inventive disposable absorbent article are improved fit and appearance, improved absorption and liquid containment properties, simpler, more efficient manufacturing process, reduction of components and material sources, and a thinner, more compact construction.
A disposable absorbent article according to the invention includes a topsheet, a backsheet, and an absorbent core disposed therebetween. At least one of the backsheet, topsheet, and absorbent core and/or a combination of these elements (e.g., a backsheet/absorbent core composite or topsheet/absorbent core composite) utilizes an absorbent composite. The absorbent composite is constructed of an absorbent layer (e.g, a low-density layer) of hydratable fine fibers in the form of microfibril obtained from cellulose or a derivative thereof, and absorbent polymer (i.e., SAP) particles bonded together by the hydratable fibers, and a nonwoven substrate (e.g., a high-density layer) supporting the absorbent layer. The absorbent layer is coated upon the nonwoven substrate.
Containment walls including leg cuffs or leg gathers may also utilize the absorbent composite. For example, the article may employ a pair of longitudinally-extending, upstanding cuffs spaced laterally from the core. Each cuff includes a folded portion of the topsheet and a longitudinally-extending absorbent composite secured within the folded portion. The longitudinally-extending absorbent composite also includes an absorbent layer of hydratable fine fibers in the form of microfibril and super absorbent polymer (SAP) particles bonded together by the hydratable fibers and a nonwoven substrate supporting the absorbent layer. In one set of embodiments, the core also includes an absorbent composite, and the core""s absorbent composite and the longitudinally extending absorbent composites of the cuffs are sections of one continuous absorbent composite structure. This composite structure is positioned about a crotch region of the article and may be adapted (e.g., by selecting appropriate SAP material specifications) to swell upon wetting so as to substantially gel-block and liquid seal the crotch region. Further, a nonwoven section of the topsheet may provide the nonwoven substrate of the absorbent composite of the containment walls and/or of the absorbent core.
In another aspect of the invention, a backsheet utilizing the absorbent composite preferably includes a low cross link SAP that is adapted to gel block upon wetting. In this way, the backsheet is breathable when dry but the absorbent layer and, thus, the backsheet, is substantially impervious when wet. Such a low cross-link SAP may be a low gel strength SAP having free swell capacities greater than about 40 g/g SAP.
In yet another aspect of the invention and in one set of embodiments, the absorbent core may be formed from a prefabricated sheet of the absorbent composite. In one embodiment, the absorbent composite has a plurality of absorbent layers (e.g., segmented) which are spaced apart from one another such that non-coated surface sections of the substrate are exposed therebetween. The non-coated surface sections form wicking zones between the absorbent layers and allow the absorbent layers room to swell, thereby preventing or minimizing gel blocking and promoting saturation of the absorbent layers. The segments of absorbent layers may be laterally spaced, elongated segments, randomly or equally dispersed (e.g., a staggered pattern) concentrations in dotted or rounded forms, or some other configuration. Preferably, the layers are concentrated or enlarged at the crotch region of the disposable absorbent article.
In one embodiment, the absorbent composite layer of the core has a corrugated configuration. This configuration is characterized by a plurality of pleats (i.e., pronounced fold lines) wherein distinct adjacent sections of the absorbent composite mutually adhere. In another embodiment, the absorbent composite is rolled about a concentration of pulp material such that the pulp concentration is disposed between two layers of the absorbent composite (i.e., xe2x80x9cnestedxe2x80x9d). Further embodiments may utilized a multi-tiered design wherein two or more absorbent composites or two or more absorbent layers are stacked (e.g., at least in the crotch region).
In yet another aspect of the invention, the absorbent composite forms the backsheet and the absorbent core. For example, the nonwoven substrate forms or is provided by the backsheet and the absorbent layer is concentrated at the crotch region to form the absorbent core. Similarly, the absorbent composite may be utilized to form at least a portion of the topsheet and the absorbent core, wherein a section of the topsheet provides the nonwoven substrate of the absorbent composite and the absorbent layer forms the core.